Rotary actuator power drawbolt for machine tool spindles



arch 28, 1967 J. DAUGHERTY 3,311,024

' ROTARY ACTUATOR POWER DRAWBOLT FOR MACHINE TOOL SPINDLES 5Sheets-Sheet 1 Original Filed Feb. 9, 1965 m G E J! N E E g g J March1967 J. DAUGHERTY 3,

ROTARY ACTUATOR POWER DRAWBOLT FOR MACHINE TOOL SPINDLES Original FiledFeb. 9, 1965 5 ShGGtS-Sht 2 iwvaw'ro Jessa DAucw-leaw March 28, 1967 J.DAUGHERTY ROTARY ACTUATOR POWER DRAWBOLT FOR MACHINE TOOL SPINDLES 5Sheets-Sheet 3 Original Filed Feb. 9, 1965 INVENTOR Jesse DAuaHEn'rv w 0w Ni 4 t MQ W $3 8 N mv l wm. $2 x m2 vb q n 5 6r a a Q I mm March 28,1967 J. DAUGHERTY ROTARY ACTUATOR POWER DRAWBOLT FOR MACHINE TOOLSPINDLES 5 Sheets-Sheet 4 Original Filed Feb. 9, 1965 INVENTOQ JesseDAUGHERTY March 28, 1967 J. DAUGHERTY ROTARY ACTUATOR POWER DRAWBOLT FORMACHINE TOOL SPINDLES 5 Sheets-Sheet 5 my 3: $2 m NL .M aw

Original Filed Feb. 9, 1965 INv Jesse DAUGHERTY 4 wog /ued, 0,4140%A-rrvs.

wm w R United States Patent M ROTARY ACTUATOR PQWER DRAWBOLT FOR Thisapplication is a continuation of my application Ser. No. 431,368, filedFeb. 9, 1965 and now abandoned.

The present invention relates to machine tools and, more specifically,to a rotary actuator power drawbolt for securing a tool in the powerdriven spindle of a machine tool. The invention finds particular, butnot exclusive, utility when embodied in a machine tool which includes anautomatic tool changing apparatus. This invention represents animprovement over the power drawbolt disclosed in my copendingapplication Ser. No. 338,108, filed Jan. 16, 1964, which issued as U.S.Patent No. 3,254,567 on June 7, 1966.

A machine tool having an automatic tool changing apparatus may beoperated under automatic control or, occasionally, under manual control.Automatic operation may, for example, be effected by numerical controlfrom a source of command signals derived from a magnetic or punchedpaper tape through a control system connected to operate the variouspower driven components of the machine. Such a machine is adapted toperform a series of machining operations with interspersed tool changingoperations, and to perform both the machining and tool changingoperations in a given program automatically from start to finish. Whilethe power drawbolt of the present invention is applicable to a widevariety of machine tool configurations, it is particularly advantageousin a machine tool incorporating automatic tool changing apparatusbecause of the severe demands made on a power drawbolt in such anenvironment.

One object of the present invention is to provide a power drawboltadapted to operate satisfactorily in a machine tool having automatictool changing apparatus,

and susceptible of positive and rapid actuation in securing the tool inthe machine tool spindle as well as in releasing the tool from thespindle.

Another object of the invention is to provide a power drawbolt of thecharacter set forth and adapted to maintain drawbolt tension withoutdepending on hydraulic or spring pressure for that purpose.

A further object of the present invention is to provide a power drawboltof the foregoing type utilizing fiuid actuating means which takeadvantage of the automatic features of the associated machine tool,resulting in substantial simplification of the mechanism.

A further object of the invention is to provide a power drawbolt of thecharacter set forth above and adapted to provide a reliable signalindication showing the device has functioned properly.

The preceding objects and advantages, as well as others, will becomeapparent from the following detailed description, taken together withthe accompanying drawings, wherein:

FIGURE 1 is a fragmentary vertical sectional view taken axially of thespindle in the headstock of an exemplary horizontal boring, drilling andmilling machine embodying the power drawbolt of the present invention.

FIG. 2 is an enlarged transverse sectional view through the inner endportion of a toolholder engageable by the power drawbolt of the presentinvention, taken in the plane of the line 2--2 in FIG. 1.

FIG. 3 is an enlarged transverse sectional view through the inner endportion of the spindle and the tool engaging 3,311,924 Patented Mar. 28,1967 end portion of the power drawbolt, taken in the plane of the line33 in FIG. 1.

FIG. 4 is an enlarged transverse sectional view through the interfittingportions of the drawbolt and toolholder during an initial stage ofengagement, takenin the plane of the line 44 in FIG. 7.

FIG. 5 is a view similar to FIG. 4 but with the drawbolt and toolholderfully engaged, taken in the plane of the line 55 in FIG. 8.

FIGS. 6, 7 and 8 are fragmentary longitudinally sectional views takenaxially of the headstock spindle, on a scale somewhat larger than thatof FIG. 1, showing sequential steps in engagement between the drawboltand toolholder.

FIG. 9 is a fragmentary longitudinal sectional view, to the same scaleas FIGS. 6, 7 and 8, illustrating the fluid power actuating mechanism ofthe drawbolt of the invention.

FIGS. 10 through 12 and 13 through 18 are transverse sectional views ofthe mechanism of FIG. 9, taken respectively in the planes of the lines10 through 12 and 13 through 18, inclusive.

FIGS. 12A and 12B are respective face views of two detent plates in themechanism of FIG. 9, taken in the planes of the lines 12A-12A and12B-12B.

FIG. 19 is a fragmentary longitudinal sectional View through themechanism shown in FIG. 9, but taken on the broken section indicated bythe line 1919 in FIG. 21.

FIGS. 20 and 21 are transverse sectional views through the mechanismshown in FIG. 19, taken in the planes of the lines 20-24) and 21-21,respectively.

While the invention is susceptible of various modifications andalternative constructions, an illustrative embodiment thereof has beenshown in the drawings and will be described below in detail. It shouldbe understood, however, that there is no intention to limit theinvention to the specific form disclosed, but, on the contrary, theintention is to cover all modifications, alternative constructions andequivalents falling within the spirit and scope of the invention asexpressed in the appended claims.

Referring more specifically t0 FIGURE 1, the invention is there shownembodied in the headstock of an illustrative machine tool such, forexample, as the one disclosed in my copending application Ser. No.338,108 mentioned above, issued as US. Patent No. 3,254,567 on June 7,1966. That machine tool happens to be a horizontal boring, drilling andmilling machine incorporating an automatic tool changing apparatus and apower drawbolt. Since the present invention is an improvement over thepower drawbolt of such machine, reference may be made to the aforesaidapplication for a more complete description of the various features ofthe machine which represent an environment in which the invention findsparticular but not exclusive utility.

It will, accordingly, be suflicient for present purposes to note thatthe illustrative boring, drilling and milling machine comprises theusual bed with a saddle and worktable slidably positionable thereon withrespect to a vertical column fixed to the bed (not shown). The machineis provided with a headstock 30 (FIG. 1) vertically movable andpositionable on guideways fixed to the vertical column. An extensiblepower driven spindle 31, rotatably and translatably supported in theheadstock 30 by a spindle sleeve 32, is adapted to receive and drive atool 34 such as the one illustrated in FIGS. 1, 6, 7 and 8. For thispurpose, the outer end portion of the spindle 31 is formed with atapered socket 35' and a pair of circumferentially spaced drive keys36'. A power drawbolt assembly 38 embodying the present invention ismounted concentrically of the spindle 31 for quickly engaging anddisengaging the tool 34 with respect to the spindle. The assembly 38comprises a I -9. on the drawbolt.

an angle of no more than 45 degrees will thereupon fully tools areindividually transported to and from the matrix by a shuttle (notshown). A tool exchange arm having one or more gripping devices 41(FIG. 1) with relatively movable opposed jaws 42, 44, is arranged toshift tools individually between the shuttle and the spindle.

The tool 34, shown in FIGS. 1, 2, 6, 7 and 8, is illustrative of thelarge selection of tools adapted to be stored in the matrix. In thisinstance, the tool comprises a milling cutter 45 mounted in a toolholder46. The latter is formed with a tapered mounting shank 48 adapted to fitthe tapered socket of the spindle. The inner end portion 49 of the shank48 has an internally threaded central bore 50' en-gageable by thethreaded outer end portion of the drawbolt 39 to hold the tool in thespindle socket 35. The toolholder 46- includes a radial flange 51situated between the cutter 45 and the tapered shank 48. The flange 51'may be advantageously utilized by the automatic tool changing apparatusas a gripping area for handling the tool. It includes a pair ofcircumferentially spaced recesses 52 adapted to receive and engage thespindle drive keys 36. The flange 51 may also have a peripheral V-shapedgroove 53 which, in some cases, may be utilized for engagement byperipheral gripping devices.

For the purpose of effecting rapid, positive engagementand disengagementbetween the tool and the drawbolt, resort is had-to a breech blockthread connection therebetween. The threads of bore 59 or" thetoolholder are, accordingly, interrupted by four circumferentiallyspaced longitudinal grooves 54 defining four threaded segmental lands 55the'rebetween (FIG. 2). In like man- 'ner, the threads of the outer endportion of the drawbolt 39 are interrupted by four circumferentiallyspaced longitudinal grooves 56 defining four threaded segmental lands 58therebetween (FIG. 3). The pitch of the threads on the drawbolt lands 58matches that of the threads on the toolholder lands 55 and the grooves54, 55 are wider than the lands 55, 58 by an appropriate clearancedistance. This arrangement permits the drawbolt and toolholder to beengaged by insertion of the drawbolt axially ,into the recess 50, asshown in FIGS. 4, 6 and 7, until the end 49 of the toolholder abuts theend of stop sleeve Rotation of the drawbolt through engage all of thethreads of the lands 55, 53, such condition being shown in FIGS. Sand 8.

Rotation of the drawbolt with the end of the stop sleeve5-9'abuttingthe'end portion 49 of the toolholder is facilitated byforming the threads of the lands 55, 58 to allow a slight amount ofaxial lost motion. Conseq-uently, the drawbolt may be rotated withoutbinding at the end of the stop sleeve 59 or ov-erstressing the engagedthreaded lands. In the present instance, a quadrifid thread connectionhas been illustrated but it will be appreciated thatother suitablentunbers of grooves and lands may be employed, the particular numberdetermining the extent of rotation required for engagement and the axialforces which may be applied to the toolholder by the drawbolt.

' For satisfactory operation in an automatic tool changing cycle,provision is made in the machine to establish the same precise angularrelationship between the toolholder, the spindle, and the threaded endof the drawbolt for each cycle. The automatic tool changing apparatusis'thus constructed sothat the position and orientation of thetoolholder are precisely controlled from the time the tool is withdrawnfrom the matrix until it is presented to the spindle by the toolexchange arm gripping device 41. To assure the desired initial angularposition of the spindle, and accordingly the drawbolt, the spindlesleeve 32 is constructed with a positioning ring 60 fixed thereon (FIG.1). The ring 60 may be formed with a radial bore 61 engageable by thetapered projecting end of a fluid actuated shot pin 62. The latter isadapted to engage the bore 51 to locate and hold the spindle inpredetermined angular position necessary to achieve proper registrationbetween the thread-ed end of the drawbolt and the threaded end of thetoolholder, and between the spindle drive keys 36 and the recesses 52 inthe toolholder flange. Rotation of the spindle is accomplished throughan appropriate drive transmission indicated diagrammatically as a box Tin FIG. 1 and connected with ring gear d4 fixed to the spindle drivesleeve 32. Control of the spindle positioning operation may be effected.after the manner set forth in the aforesaid application Ser. No.338,108, issued as US. patent No. 3,254,567 on June 7, 1966.

In order to minimize the necessary movements of the tool changingapparatus, and to make optimum use of existing mechanism, the spindlemay be extended from a pie-engagement retracted position, as viewed inFIG. 1, to a position shown by the dotted lines in that figure where thetool shank 48 is loosely seated in the tapered socket 35. When thisposition is achieved, keys 36 are received in the keyway slots 52 and itwill further be observed that the threaded end portion of the drawbolt39 is received in the threaded bore 59.

Axial extension and retraction of the spindle 31 is accomplished bymeans of a ram 65 supported within a headstock 3d. The ram is adapted totransmit an axial thrust from a suitable feed transmission (not shown)to the spindle for feed or positioning purposes. In the latter event,various stop abutments between the headstock frame and the ram may beused for determining selected axial positions of the latter. The innerend portion of the spindle 31 is rotatably coupled to the ram 65 foraxial translation therewith by means of a pair of thrust bearings 66.The latter are locked in place on reduced diameter end portion 68 of thespindle by means of a retainer nut 69. The bearings 66 are lockedaxially in the ram 65 between spacer collar 70 and retainer collar 71fixed to the spindle end of the ram. The ram also houses drawboltactuating mechanism 46] as well as the thrust bearing connection withthe spindle. For this purpose, the ram is formed with a steppedlongitudinal bore 72.

The actuating mechanism 49 is fashioned as a generally cylindrical unithoused telescopically within the bore 72 between the end face 74 of thespindle and an internal shoulder 75 in the ram. The bore 72 is ofsulficient length to accommodate the unit 40 with a limited amount ofend clearance or float, such, for example, as 0.009, between the endface '74 and the shoulder 75. The mechanism 40, while retained axiallywithin the bore 72 with limited axial motion relative to the spindle, isbodily connected to the latter for direct rotation therewith. This isaccomplished in the present instance by means of a relatively flatdiametrically extending key 76' which engages a corresponding keyway inthe end face 74 of the spindle (FIGS. 9 and 18). The mechanism; 40 alsoincludes a hub 73 received in an axial bore 79 in the inner end portion63 of the spindle.

Provision is made in the assembly 38 for effecting positive actuation ofthe drawbolt 39 in two sequential steps, both on engagement anddisengagement of the toolholder. For engagement or clamping these twosteps are first, effecting full threaded engagement with the toolholderand second, applying axial tension to seat the tapered shank of thetoolholder firmly in the spindle soci'et. For disengagement orunclamping, these steps are reversed and the additional step of an axialthrust to break thev frictional contact between the toolholder and thespindle socket is interposed.

The foregoing is accomplished by utilizing in the actuating mechanism 40two rotary fluid actuators mechanically interlocked for sequentialoperation on the drawbolt 39. The mechanism 40 is, accordingly,constructed as a laminated unit comprising first and second hydraulicmotors 80, 81 with an interlock section 82 interposed between. The motor80 in this case comprises a stator 84, a vane-type rotor 85, and a pairof end caps 86, 88 secured together as by means of a plurality ofcircumferentially spaced retaining screws 39. By the same token, themotor 81 comprises a stator 90, a vane-type rotor 91, end caps 92, 94,and a plurality of circumferentiallyspaced retaining screws 95. Theentire assembly comprising the motors 80, 81 and the interlock section82 is secured together as a unitary assembly by means of a plurality oflong assembly screws 96. The unit is telescoped over the inner endportion of the drawbolt 39 and connected With it so as to achieve thesequential operation mentioned above.

The motor 80 has a direct connection with the drawbolt 39. For thispurpose, that portion of the drawbolt extending into the motor 80 isformed with longitudinal splines 98 which mate with correspondinglongitudinal splines in the bore of the rotor 85. These splines continueinto the interlock section 82 and mate with corresponding splines in adetent plate 99.

The motor 81 has a lost motion connection with the drawbolt 39. In thisinstance, the portion of the drawbolt 39 extending through the motor 81is formed with a plurality of threads 100 which engage the threaded boreof a tensioning nut 101. The outer periphery of the latter is formedwith longitudinal splines 102 which mate with corresponding longitudinalsplines in the bore of the rotor 91. The nut 101 extends beyond themotor 81 and partially into the interlock section 82. This extendedportion of the nut carries a detent plate 104 having correspondingsplines which engage those of the nut. The opposite end of the nut 101is adapted to bear against a pair of thrust washers 105 situated in theend cap 92.

Turning now to the interlock section 82 (FIGS. 9, 12, 12A, 12B), it willbe noted that the latter in this instance comprises a fixed cylindricalpartition 106 having a central bore 108 sutficiently large in diameterto clear the drawbolt 39. The partition 106 has annular recesses in itsrespective end faces to receive the detent plates 99, 104 withsuflicient clearance to permit rotation of the same. The partition 106may also have a further annular recess 107 to accommodate the end of thenut 101. The central annular portion 109 of the partition 106 is formedwith a plurality of circumferentially spaced axial bores 110, in thiscase three in number spaced 120 apart. Each of the bores 110 contains apair of hardened steel balls 111 having a total diameter somewhatgreater than the axial length of the bores 110. The detent balls 111thus tend to project axially from one end or the other of the bores 110.

The detent plates 99, 104 are formed with corresponding sets of recesses112, 114, respectively, in their respective faces adjacent the annularportion 109 of the partition 106. In the operation of the mechanism 40,the plates 99, 104 are adapted to be brought into registrationalternately with the bores 110 and detent balls 111. Such registrationhas the effect of locking the registered plate against rotation whilepermitting the other plate to be rotated. In this instance, the detentplates 99, 104 are initially given angular positions 45 apart.

By reason of the foregoing arrangement, when the drawbolt mechanism 40is in its initial unclamped position, indicated in FIG. 9, the detentballs 111 are registered with the recesses 114 of the plate 104. Thisleaves the detent plate 99 and its associated motor 80 free to rotatebut locks the plate 104-and its motor 81 against rotation. Uponapplication of fluid pressure to the rotor of the motor 80, the latter,together with the drawbolt 39 and the detent plate 99 is rotated throughan angle of 45. This brings the recesses 112 of the plate 99 intoregistration with the bores 110 and detent balls 111. The halls arethereby permitted to regress into the recesses 112 of the plate 99,unlocking the plate 104 and its associated motor 81. Upon application offluid pressure to the rotor 91 of the motor 81 under such conditions,the latter and the nut 101 splined thereto rotate through an angleapproaching 112. Because of the engagement of the nut 101 with thethreads 100 of the drawbolt, the nut 101 tends to shift axially to theleft as viewed in FIG. 9 and to press against the thrust washers 105.This shifts the drawbolt axially to the right by an amount which may,for example, be 0.008", tensioning the drawbolt 39 and firmly seatingthe shank of the toolholder in the spindle socket.

For unclamping, the foregoing sequence is reversed. The interlockconnections just described permit reverse rotation of the motor 81 torelease tension on the drawbolt 39 while precluding rotation of themotor 80. Such action drives the nut 101 in the opposite directionrelative to the threads 100 and presses the right-hand end of the nut,as viewed in FIG. 9, against recess 107 in the annular portion 109 ofthe partition. This provides a reaction axially of the drawbolt,producing an impact between the end of the stop sleeve 59 and the innerend portion of the toolholder, breaking the toolholder shank loose fromthe tapered spindle socket. At that point, the detent plate 104 has itsrecesses 114 in registration with the bores and detent balls 111,permitting rotation of the detent plate 99 and the motor 80 through areversing angle of 45 to disengage the threaded portions of the drawboltand toolholder, leaving the mechanism in unclamped position as shown inFIG. 9.

Fluid pressure for actuating the mechanism 40 may be supplied from anappropriate source such as motor driven pump P and tank T (FIG. 19).Supply and drain lines from this unit are connected to the mechanism 40via a four-way, two position, solenoid operated hydraulic valve 116. Thelatter is connected to the ram 65 via flexible conduits 118, 120. Theoperation of the valve 116 is such that, in one position, the conduit118 will be connected directly with the pressure side of the pump P andthe conduit 120 will be connected with the drain to tank T. In thealternate position of the valve 116, the connections of the lines 118,120 will be reversed.

As shown in FIG. 19, the conduit 118 is connected to a fluid passage 119running longitudinally of the ram 65. The passage 119 has a laterallyenlarged portion housing a slidable coupling plunger 122 with alongitudinal bore 119a therein communicating directly with the passage119. The coupling plunger 122 is normally urged away from the mechanism40 which rotates with the spindle. This is done by means of a peripheralspring 124 interposed between a fixed collar 125 in the enlarged part ofthe passage 119 and a lock ring 126 on the inner end of the plunger. Theopposite end of the plunger is provided with a check valve 128. Uponstopping of the spindle 31 and the mechanism 40 in the predeterminedrotary index position for clamping or unclamping a tool, such positionbeing determined by the shot pin 62 (FIG. 1), the coupling plunger 122of passage 119 has its bore 119a aligned with main fluid passage 129 inthe mechanism 40. When pressure is applied to the passage 119 and bore119a, the end face of the plunger 122 is forced into sealing contactwith the end of the actuating mechanism 40. At that point, the checkvalve 128 opens, establishing communication between passage 119, bore119a and passage 129. The effective piston area of the plunger 122 issuflicient to maintain such sealing contact and communication as long aspressure is applied.

In like manner, the passage 121 is laterally enlarged and provided withan identical coupling plunger 130 having a longitudinal bore 121a. Theplunger 130 is nor- .mally biased awayfrom the mechanism 411 by means ofspring 131. Application of pressure fluid to the passage open andtransmit fluid to the passage 132.

During operation of the mechanism 49 to clamp or unclamp the drawbolt,only one of the coupling plungers .122, 131) will be in pressure sealingContact, leaving one of the passages 129, 132 open to drain. Also,during rotation of the spindle and mechanism 40 incident to machiningoperations, neither plunger will be in sealing .contact and bothpassages 129, 132 will be open to drain.

Unpressurized fluid thus tends to accumulate in the main bore 72 of theram. To discharge such accumulated fluid 7 from the ram, the lattermaybe provided with one or more drain passages 135, 136 (FIG. 19).

With the mechanism 46 in the condition indicated in FIGS. 9 and 19,actuation of the solenoid valve 116 to connect the passage 119 to thepressure side of the pump P and the passage 121 to the tank T willinitiate a drawbolt clamping cycle. In such event, pressure fluid issupplied to the passage 119, bore 11%, and passage 129. It

passes from the latter into the annular passage 138 in the stator 84 ofthe motor 8@ and from thence via ports '139, 140 into rotor chambers141, 142 (FIG. 16). Rotor chambers 144, 145 on the opposite side of thevanes of rotor 85 are connected to drain or tank via ports his,

.148, annular passage 149, passage 132, and drains 135,

136 (FIGS. 16, 17 and 19). Under these conditions, the rotor 85 of motor84 and the drawbolt 39 rotate clock- -wise (as viewed in FIG. 16)through an angle of substantially 45 to effect engagement between thethreaded lands 5110f the drawbolt and the threaded lands 55 of thetoolholder. Such rotation is also imparted to the detent plate 99associated with the motor 80, bringing the recesses 112 of the plate 99into register with the bores 11!) and detent balls 111. This unlocks thedetent plate 164 and rotor 91 of motor 81.

To further insure proper sequence of motor operation, a hydraulicinterlock is utilized between the motors 8t and 81 whereby pressurefluid is precluded from entering the tensioning motor 81 until thethread interlocking motor 811 has first been energized. This comprises apressure fluid connection to the motor 81 via ports 150, 151 in themotor 80 uncovered by the angular advance of rotor 85 only after partialcompletion of its 45 clockwise movement (FIG. 13). The ports 156, 151are connected 7. with an'annular passage 152 within the end cap 86 ofthe motor 89. The latter in turn is connected with a longitudinalpassage 154, isolated from the passage 129 by ,check valve 155, and anadditional longitudinal passage 156 (P163 19 and 11). The passages 154,156 are adapted to conduct pressure fluid to rotor chambers 158, 159 ofthe motor 81 via ports 16%, 161 (FIGS. 11 and '10). At the same time,the opposite rotor chambers 162,

164v of the motor 81 are connected to drain via the ports 165,166 andthe passages 16%, 169 (FIG. 11). With the foregoing hydraulic circuitestablished, the rotor 91 of the motor 81 Will rotate counterclockwise,as viewed in FIG. 10, through an angle approaching 112. Since the rotorhas a splined connection with the nut 101, the

latter will rotate bodily with the rotor 91 to effect tensioning of thedrawbolt in the manner previously described.

When the valve 116 is operated to pressurize the passage 121 and connectthe passage 119 to drain, the motors 81,80 will be reversed sequentiallyto release or unclamp the drawbolt 39. In the latter event, the plunger130 effects a pressure seal and pressurizes the passage 132 while thepassage 129 is open to drain. Passage 132 connects with annular passage149 (FIG. 17) which,

v in turn, connects via spur passages 1'79, 171 with passages 168, 169leading to rotor chambers 162, 164 of the tensioning motor 81. Passage14-9 also connects to rotor chambers 144, 14-5 of the motor 81) viaports 172, 174 (FIG. 15). Since the motor $11 is locked by its detentplate 99 at this time, the applied fluid pressure will act on the rotor91 of tensioning motor 81, causing counterclockwise rotation of therotor 91 so that the nut 101 is operated to release tension on thedrawbolt. After drawbolt tension is released, further rotation of therotor 91 causes the nut 1'91 to move to the right, thereby seatingagainst the annular recess 11117 in the partition 1116. This produces anendwise thrust on the drawbolt which breaks the frictional contactbetween the shank of the toolholder and the spindle socket and alsorelieves the pressure on the interengaged threaded lands of the drawboltand toolholder. Rotation of the rotor 91 brings the recesses 114 ofdetent plate 1114- into registration wtih the passages 111) and detentballs 111, thereby unlocking the detent plate 99 of motor Fluid pressurefrom the main passage 132 is now effective through ports 172, 174 toturn rotor of motor 80 counterclockwise through an angular displacementof 45. The rotor 85, being splined on the drawbolt 39, carries thelatter through an angular displacement of 45 and leaves it in positionfor disengagement from the toolholder.

Provision is made in the drawbolt actuating mechanism 40 for generatinga signal to confirm proper engagement of the drawbolt with thetoolholder of an associated tool. This signal may, for example, beutilized in a safety interlock to preclude operation of the spindledrive until the drawbolt is properly engaged with the toolholder. Infurtherance of such objective, a proximity switch 175 is mounted in therearward portion of the ram 65 (FIGS. 9, l9 and 20). The switch may beof various forms and in this instance happens to be of the type whichproduces a signal upon angular alignment of an oblong armature 17orotatably mounted in proximity to the switch. The armature 176 is fixedto a rearward extension 178 of the drawbolt adjacent a large flange 179secured to the drawbolt by pin 1%. The switch 175 is verticallyoriented. With the drawbolt in unclamped condition, as shown in FIGS. 9and 19, the armature is disposed at an angle of 45 with the vertical.

The switch 175 is fixed to a carrier 1S1 slidably mounted in a bore 132axially aligned with the drawbolt and situated in the rearward portionof the ram (FIGS. 9 and 19). The carrier 181 has a forward flange 184-and a rearward flange 185 retaining it in the bore 182. A plurality ofcircumterentially spaced guide plungers 186 fixed to the rear flange 185key the carrier 181 against rotation in the bore 182. Springs 138,acting between the ram body and the plungers 13d, serve to bias thecarrier 181 away from the drawbolt (PEG. 9).

The carrier is adapted to be shifted toward the drawbolt so as toovercome the bias of springs 13% whenever fluid pressure is applied tothe passages 119 or 121. This is accomplished by means of two smallcylinders 139 in the ram body respectively connected by radial passages19! with the passages 119, 121 (FIGS. 19, 21). Each of the cylinders 189has a plunger 191 which bears against the forward flange 134 of thecarrier. Semi-circular buffer springs 19?; fixed to the flange 184(FIGS. 9, 19 and 20) cushion the movement of the carrier toward thedrawbolt under fluid pressure and also space the switch 175 properly inrelation to the armature by reason of their abutment with the drawboltflange 179.

As noted earlier herein, clamping of the drawbolt involves the essentialstep of rotating it 45 to engage its threaded lands 58 with the threadedlands 55 of the toolholder. This also serves to rotate the armature 176through 45, bringing it into alignment with the proximity switch 175 andthus producing a signal confirming proper engagement of the drawboltwith the toolholder.

I claim as my invention:

1. A power drawbolt assembly for releasably securing a tool in thesocket of a machine tool spindle, the tool having a toolholder with abore therein and breech block type threads in the bore, the combinationcomprising a drawbolt disposed longitudinally of the spindle and havingan outer end portion projecting into the socket, said outer end portionhaving breech block type threads engageable with those of thetoolholder, a first rotary fluid actuator connected with said drawboltand adapted to effect rapid engagement of said threads on said drawboltand the toolholder, a second rotary fluid actuator connected with saiddrawbolt and adapted to tension the same axially to seat the toolholderin the spindle socket, and means for interlocking said first and secondactuators for operation in sequence.

2. A power drawbolt assembly for releasably securing a tool in thesocket of a machine tool spindle, the tool having a toolholder with athreaded bore, the combination comprising a drawbolt disposedlongtitudina-lly within the spindle and having a threaded end portionengageable with said bore, a first fluid actuator connected to saiddrawbolt and adapted to efiect threaded engagement between said drawboltand the toolholder, a second fluid actuator connected with said drawboltand adapted to exert an axial thrust on said drawbolt to seat thetoolholder in the spindle socket, and means for interlocking saidactuators for operation sequentially.

3. A power drawbolt assembly for releasably securing a tool in thesocket of a machine tool spindle, the tool having a toolholder withbreech block type threads, the combination comprising a drawboltdisposed longitudinally of the spindle and having an outer end portionprojecting into the socket, said outer end portion having breech blocktype threads engageable with those of the toolholder, a first rotaryfluid actuator directly connected with said drawbolt and adapted toeffect rapid engagement and disengagement of said drawbolt andtoolholder threads, a second rotary fluid actuator connected with saiddrawbolt and adapted to tension the same axially to seat the toolholderin the spindle socket and to release said axial tension to unseat thetoolholder from the spindle socket, and means for interlocking saidfirst and second actuators for operation in sequence on engaging saidtoolholder.

4. A power drawbolt assembly for releasably securing a tool in thesocket of a machine tool spindle, the tool having a toolholder withrapid coupling threads thereon, the combination comprising a drawboltdisposed longitudinally within the spindle and having an end portionwith rapid coupling threads thereon engageable with those of thetoolholder, a first rotary fluid actuator connected to said drawbolt andadapted to efiect threaded engagement and disengagement between saiddrawbolt and the toolholder, a second rotary fluid actuator connectedwith said drawbolt and adapted to exert an axial thrust on said drawboltto seat the toolholder in the spindle socket and to unseat thetoolholder from the spindle socket, and means for interlocking saidactuators for operation in sequence.

5. In a machine tool, the combination comprising a power driven spindlewith a tool socket therein, a toolholder adapted to seat in said socket,said toolholder having a bore therein with a plurality ofcircumferentially spaced threaded lands, a drawbolt disposedlongitudinally of said spindle and having an end portion projecting intosaid socket with a corresponding plurality of threaded lands thereon,said threaded lands of said toolholder and said drawbolt beingengageable upon limited relative rotation therebetween, and a rotaryfluid actuator mechanism constructed and arranged to provide sequentialrelative rotational mo tion and axial tensioning of said drawbolt toseat said toolholder in said socket.

6. In a machine tool, the combination comprising a power driven spindlewith a tool socket therein, a toolholder having a shank adapted to bereceived in saidv spindle socket, a drawbolt longitudinally disposed insaid spindle, said drawbolt having a peripherally segmented threadedportion at one end thereof, means defining a complementary segmentedthreaded bore in said toolholder shank, means on said machine tool foraligning said toolholder shank and said draw-bolt to permit insertion ofsaid drawbolt therein with the threaded segments thereof alternatingwith the threaded segments of said toolholder bore, a first rotary fluidactuator connected to rotate said drawbolt to engage the respectivethreaded segments of said drawbolt and said toolholder bore, and asecond rotary fluid actuator coupled with said first actuator and saiddrawbolt for axially tensioning the latter and securing said toolholderin said spindle.

7. A power drawbolt assembly for releasably securing a tool in thesocket of a machine tool spindle, the tool having a toolholder with athreaded bore, the combination comprising a drawbolt disposedlongitudinally within the spindle and having a threaded end portionengageable with said bore, a first rotary fluid actuator directlyconnected to another portion of said drawbolt and adapted to eifectthreaded engagement between said drawbolt and toolholder, a nutthreadedly connected to still another portion of said drawbolt, a secondrotary fluid actuator directly connected with said nut and adapted toexert thereby an axial thrust on said drawbolt to seat the toolholder inthe spindle socket, and means for interlocking said actuators foroperation sequentially.

8. In a machine tool, the combination of a power driven spindle with atool socket therein, a toolholder adapted to seat in said socket, saidtoolholder having a bore therein with a plurality of circumferentiallyspaced threaded lands, a drawbolt disposed longitudinally of saidspindle and having an end portion projecting into said socket with acorresponding plurality of threaded lands thereon, said threaded landsof said toolholder and said drawbolt being engageable upon limitedrelative rotation therebetween, a rotary fluid actuator mechanismconstructed and arranged to provide sequential relative rotationalmotion and axial tensioning of said drawbolt to seat said toolholder insaid socket, and electrical interlock means responsive to angularengagement of said threaded lands on said toolholder and said drawboltfor governing the application of power to said spindle.

9. A power drawbolt assembly for releasably securing a tool in thesocket of a rotatable and translatable machine tool spindle, the toolhaving a toolholder with a threaded bore, and comprising, incombination, a drawbolt disposed longitudinally within the spindle andhaving a threaded end portion engageable with said bore, a first rotaryhydraulic actuator directly connected to said drawbolt and adapted toeffect threaded engagement between said drawbolt and the toolholder, asecond rotary hydraulic actuator connected with said drawbolt andadapted to exert an axial thrust thereon to seat the toolholder in thespindle socket, and means for hydraulically interlocking said actuatorsfor operation sequentially.

No references cited.

WILLIAM W. DYER, JR., Primary Examiner,

GERALD A. DOST, Examiner,

1. A POWER DRAWBOLT ASSEMBLY FOR RELEASABLY SECURING A TOOL IN THE SOCKET OF A MACHINE TOOL SPINDLE, THE TOOL HAVING A TOOLHOLDER WITH A BORE THEREIN AND BREECH BLOCK TYPE THREADS IN THE BORE, THE COMBINATION COMPRISING A DRAWBOLT DISPOSED LONGITUDINALLY OF THE SPINDLE AND HAVING AN OUTER END PORTION PROJECTING INTO THE SOCKET, SAID OUTER END PORTION HAVING BREECH BLOCK TYPE THREADS ENGAGEABLE WITH THOSE OF THE TOOLHOLDER, A FIRST ROTARY FLUID ACTUATOR CONNECTED WITH SAID DRAWBOLT AND ADAPTED TO EFFECT RAPID ENGAGEMENT OF SAID THREADS ON SAID DRAWBOLT AND THE TOOLHOLDER, A SECOND ROTARY FLUID ACTUATOR CONNECTED WITH SAID DRAWBOLT AND ADAPTED TO TENSION THE SAME AXIALLY TO SEAT THE TOOLHOLDER IN THE SPINDLE SOCKET, AND MEANS FOR INTERLOCKING SAID FIRST AND SECOND ACTUATORS FOR OPERATION IN SEQUENCE. 